Method and arrangement for increasing the speed of load changes in groups of power plants

ABSTRACT

A method of increasing the load change velocity of power plant blocks, characterized in that during the dynamic operation of the power increase, the tapped quantities of stream for the high pressure preheater which in stationary operation are withdrawn through withdrawing steam conduits from the turbine are throttled by steam ahead of the superheater or the end superheater of the steam generator or are stopped completely.

United States Patent Klan: Knida Nochen Ueber Engelsltirehen, Germany 776,536

Nov. 18, 1968 June 22. 1971 Brown, Boveri & Cie

Mannheim, Germany Nov. 18, 1967 Germany Inventor Appl. No Filed Patented Assignee Priority METHOD AND ARRANGEMENT FOR INCREASING THE SPEED OF LOAD CHANGES IN GROUPS OF POWER PLANTS 4 Claims, 1 Drawing Fig.

521 US. Cl

60/67, 60/104 Folk 7/16 60/67, [04,

Field ofSeareh [56] References Cited UNITED STATES PATENTS 3,1 73,267 3/ l 965 Takeda 60/67 3,314,237 4/1967 Strohmeyer 60/67 X 3,413,809 12/1968 Bredtschneider etal. 60/104 Primary Examiner-Carroll B. Dority, Jr. AttameyWalter Becker ABSTRACT: A method of increasing the load change velocity of power plant blocks, characterized in that during the dynamic operation of the power increase, the tapped quantities of stream for the high pressure preheater which in stationary operation are withdrawn through withdrawing steam conduits from the turbine are throttled by steam ahead of the superheater or the end superheater of the steam generator or are stopped completely.

METHOD AND ARRANGEMENT FOR INCREASING THE SPEED OF LOAD CHANGES IN GROUPS OF POWER PLANTS The present invention relates to a method of, and arrangement for increasing the load-changing speeds in groups of power plants.

Groups of power plants operating with constant pressure are limited as to the speed at which they can change from lower loads to higher loads. This is due to the time required for loading the system. This time is determined by the control delay in the firing and by the time for the accumulation of the entire system.

For influencing the load-changing speeds of power plant blocks, a method has become known according to which the quantities of withdrawn steam for the intermediate and lowpressure preheaters are changed by a control of the feed water flow through these preheaters. In this way, the quantity of steam available in the turbine is changed and thereby the output power. This known method, however, has the drawback that the thus-obtained immediate power change is rather limited by the relatively small quantities of withdrawn steam and their low useful pressure drop. Furthermore, the feed water flow through the high and intermediate pressure preheaters depending on the desired increase on the load is controlled downwardly, for instance, up to valve zero. The feed water flow from the steam generator must, however, correspond continuously and not to the respective load. Thcrefore, the feed water flow can be effected only between two accumulators under low pressure which, with regard to the circuit, are located ahead of the feed pump. All of the high-pressure preheaters can in this way not be included in the circuit.

it is, therefore, an object of the present invention to provide a method and arrangement of the above-mentioned general type which will overcome the drawbacks outlined above.

it is another object of this invention to provide a method and arrangement for increasing the speed in load changing in blocks of power plants, which will permit considerably higher load changing speeds alone or with the additional employment of the above-mentioned method.

These and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawing, illustrating by way ofexample a circuit according to the present invention.

The method according to the present invention for increasing the load-changing speed in power plant blocks is characterized primarily, in that during the dynamic process of increasing the load, the tapped quantities of steam for the highpressure preheaters, which quantities are in a stationary operation withdrawn from the turbine through the steam withdrawing lines, are throttled by the reduced steam withdrawn ahead of the superheater or the end superheater of the steam generator, or are completely stopped. These withdrawn quantities of steam are relatively considerably greater, and through a portion of the drop in the preceding machine and the total drop of the post turbine are adapted to expand to such an extent that such high immediate power change will be possible.

According to a further development of the present invention, the steam withdrawn ahead of the superheater or the end superheater of the steam generator is reduced in reducing stations to the corresponding top pressure and is subsequently conveyed to the pertaining high pressure preheaters. The reducing stations may expediently be arranged directly in front of the entry of the additional steam lines into the steam withdrawing conduits.

By means of the reducing stations of these additional steam lines, it is possible in an advantageous manner to control the tap steam flow from the turbinev A further advantage of the method according to the invention consists in that when load changes occur, the feed water entrance temperature can be continued in conformity with the last stationary condition. Furthermore, a dropping of the steam temperature at the superheater exit will be avoided. The quantities of steam displaced from the turbine by the steam withdrawal from the steam generator may expand further in said turbine and bring about an immediate load increase.

Referring now to the drawing in detail: the high-pressure preheaters 1,2, and 3 are respectively by means of steamwithdrawing lines 4, 5, and 6 connected to the turbine set 7, 8. The lines or pipes 4, 5 may lead to the high-pressure turbine 7 and the line or pipe 6 may lead to the low-pressure turbine 8. The withdrawing lines 4 and 6 may respectively have interposed therein deheaters 9 and [0. Connected to the steamwithdrawing line 4, 5, and 6 is a steam line [3 which at 11 branches off ahead of the superheater 12. The connection of line 13 with lines 4, 5, and 6 is respectively effected through lines 14 and t5 and direction connection of the line IS with line 6. In the auxiliary steam lines l4, [5 there are provided reducing stations 16 and [7. At the end of the steam line 13 which leads directly into the line 6 there is provided a reducing station 18 shortly ahead of the point where line 13 leads into line 6.

As will be seen from the drawing, there is furthermore provided a line 19 which comprises the condenser 20 and the condensate pump 2!. The circuit shown in the drawing also comprises a low pressure preheater 22, a feed water condenser 23 and the feeding pump 24. The steam generator proper 25 is represented by the economizer 27, the evaporator 26, and the superheaters l2 and 28.

If an increase in the load is required, simultaneously an increase in the firing power is effected and the feed pump power is increased while the reducing valves l6, l7, [8 in the withdrawing conduit 13 coming from the steam generator 25 are opened up. The power furnished by the turbine set 7, 8 increases, inasmuch as the withdrawing steam flows of the uppermost tapping stations expand further in the turbine. The additional quantity of heat required during this dynamic process, in addition to the higher fire power is bridged by releasing from storage the heat in the steam producer. The pressure ahead ofthe turbine 7 increases to a limited extent in view of the higher steam flow through the turbine in conformity with the steam cone law. If the required higher power is to be maintained, this control operation is continuously stopped and, more specifically, by the fact that the reducing stations l6, l7, 18 are closed again and the firing rate is reduced to the firing power necessary for the new load point while the feed pump feeds the quantity of feed water required by the pertaining load point.

Since with a considerable increase in the firing power, the available heat for the heating surfaces located further in the rear of the steam producer is increased beyond the proportional relationship, the method according to the present invention may be used not only for controlling the frequency, but also with increased loads in the sense ofa timewise shortening of this process.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawing, but also comprises any modifications within the scope of the appended claims.

What [claim is:

l. in a power plant having a steam generator including a high-pressure preheater and a superheater connected in series, means connecting said superheater to a multistage turbine, conduit means for tapping steam from an intermediate stage of said turbine and supplying it to said high pressure preheater, means for conveying steam from between said highpressure preheater and said superheater and supplying the steam to said conduit means to throttle steam tapped from said turbine as desired.

2. In a power plant having a turbine power plant block, a steam generator including a high-pressure preheater and a superheater connected in series, means connecting said superheater to the turbine power plant block, conduit means for conveying steam from said power plant block to said high pressure heater, second conduit means connected between said high pressure heater and said superheater to said first conduit means and comprising reducing stations to regulate 3 4 the flow of steam in said first conduit means from said power means to said high-pressure preheating means. P 4. In a power plant according to claim 1, including reducing 3. ln a power plant according to claim 2, a low-pressure preheater means, first pump means interposed between said lowpressure preheater means and said high'pressure preheater 5 means for feeding feed water from said low-pressure preheater the steam in said second conduit means to the pressure of the steam in said first conduit means. 

1. In a power plant having a steam generator including a highpressure preheater and a superheater connected in series, means connecting said superheater to a multistage turbine, conduit means for tapping steam from an intermediate stage of said turbine and supplying it to said high pressure preheater, means for conveying steam from between said high-pressure preheater and said superheater and supplying the steam to said conduit means to throttle steam tapped from said turbine as desired.
 2. In a power plant having a turbine power plant block, a steam generator including a high-pressure preheater and a superheater connected in series, means connecting said superheater to the turbine power plant block, conduit means for conveying steam from said power plant block to said high pressure heater, second conduit means connected between said high pressure heater and said superheater to said first conduit means and comprising reducing stations to regulate the flow of steam in said first conduit means from said power plant block.
 3. In a power plant according to claim 2, a low-pressure preheater means, first pump means interposed between said low-pressure preheater means and said high-pressure preheater means for feeding feed water from said low-pressure preheater means to said high-pressure preheating means.
 4. In a power plant according to claim 2, including reducing the steam in said second conduit means to the pressure of the steam in said first conduit means. 